Changhoon Seo

Vibrotactile Display for Driving Safety Information

Vehicle driving support systems such as navigation systems and dead-angle warning systems make us safer and more comfortable. These kinds of systems provide only visual and auditory information. However, visual driving support systems are restricted in drivers field-of-view and auditory warning signals can lose in radio music, engine noise, or conversation noise. Tactile displays using vibration motors can provide useful information in spite of restricted field-of-view and noisy environment. It may quickly draw the attention of the driver when important events occur: for instance, collision warning and directional cues. These intuitive and quick cues may be combined together with the visual and auditory display to give multimodal feedback to the driver. In this paper, we present a vibrotactile display device for providing safety information to drivers. User studies with the vibrotactile device on the top of the foot show 86.7% recognition rate for alphabet characters after some training and 83.9% for providing driving safety information

Immersive live sports experience with vibrotactile sensation

This paper presents a vibrotactile display system designed with an aim of providing immersive live sports experience. Preliminary user studies showed that with this display subjects were 35% more accurate in interpreting an ambiguous visual stimulus showing a ball either entering or narrowly missing a football net. About 80% of subjects could judge the correct ball paths in the presences of ambiguous visual stimuli. Without the tactile display, only 60% correct paths are judged from the visual display.

Stable bilateral teleoperation using the energy-bounding algorithm: Basic idea and feasibility tests

This paper presents basic idea and feasibility test results of the energy-bounding algorithm (EBA) for bilateral teleoperation. Various test results for free, contact, and abrupt motions show that the EBA can ensure stable bilateral teleoperation for the fairy large constant/variable time delays (2.5 sec for free motion and 300 msec for contact motion). In addition, the EBA with holding previous data strategy can achieve stable teleoperation when some packet drop is occurred during the data transmission.

A Preliminary Test for Bilateral Teleoperation Using Energy Bounding Algorithm

This paper presents a preliminary tests results for bilateral teleoperation using the energy bounding algorithm that is already proposed for stable haptic interaction control. The preliminary experimental results show that the energy bounding algorithm may generate stable bilateral teleoperation regardless of the amount of constant/variable time delay. The test results are qualitatively compared with the other existing results.

A Survey of Haptic Control Technology

Haptics technology allows one to interact with virtual environments, augmented environments, and real environments providing tactual sensory information. Science and technology of haptics can in general be classified into three groups: machine haptics, computer haptics, and human haptics. This paper surveys the state-of-the-art of haptic control technology for virtual environments and teleoperation (real environments) and then proposes possible future research directions in the following areas: haptic stability control, bilateral teleoperation control, and stability enhancement control.

A Multirate Energy Bounding Algorithm for High Fidelity Stable Haptic Interaction Control

This paper presents multirate energy bounding algorithm to provide high fidelity stable haptic interaction. Stable haptic interaction control algorithms such as virtual coupling or time-domain passivity algorithm has been studied by many researchers. For slowly-simulated virtual environments, however, the deterioration of realistic haptic feeling is unavoidable because these algorithms require high update rate. For high fidelity haptic interaction, we propose multirate approach that separates haptic thread and low-level control thread. A haptic thread carries out calculating the virtual environments force at slow rate while low-level control thread executes determining the actuator force by the energy bounding algorithm at high update rate. Experiments using commercial haptic device have been performed to show the efficiency of the proposed algorithm. As a result, we confirmed that the response was stable and displayed stiffness was much increased even though the haptic rendering rate was slow

An energy-bounding approach to rate-mode bilateral teleoperation of remote vehicles in constant time-delayed environments

This paper presents an energy-bounding approach to a rate-mode bilateral control of remote vehicles in order to guarantee the system stability in constant time-delayed telecommunication environments. The velocity error between desired and actual remote vehicle velocities is reflected in term of force in order to maintain desired velocities by the operator both during the normal driving in obstacle-free environments and when colliding with a high impedance wall. A rate-mode energy-bounding algorithm is devised for these teleoperation scenarios in order to sensitively feel the velocity difference while keeping interaction stability. Effectiveness of the proposed approach is shown by some experimental results in the simulated constant time-delayed environments for vehicles not only in free space but also in contact motions.

Enhancing rate-hardness of energy-bounding algorithm by considering Coulomb friction of haptic interface

In haptics, both transparency and stability are major requirements for providing realistic feeling of virtual objects. The crisp contact feeling at the instant of touch with high impedance walls is necessary especially for proper identification and manipulation of virtual objects. This paper presents a new passivity condition that explicitly includes Coulomb friction effects. Moreover, the energy bounding algorithm incorporating Coulomb friction effects shows that the viscous damping of the haptic device affects the maximum displayable stiffness in steady-state and that the Coulomb friction of the device contributes to temporarily enhance rate-hardness in initial transient responses. Experimental results are presented for showing effectiveness of the proposed derivation and control law.

An energy bounding approach for directional transparency in multiple degree-of-freedom haptic interaction

This paper presents an energy bounding approach (EBA) to enhance directional transparency while guaranteeing stability for multiple degree-of-freedom (DOF) haptic interaction. It was observed that the passivity condition for multiple ports may lead to some oscillations in some coordinate directions even though total energy is positive. The passivity condition, therefore, needs to be applied to each orthogonal coordinate. For guaranteeing stability in each orthogonal coordinate, the EBA is applied. For multiple-dof haptic interaction, however, the EBA in each coordinate may cause a problem that the direction of the rendered force vector is distorted. This problem can easily be solved by projecting the direction of the rendered force vector on its original direction. The validity of the proposed algorithm is shown by some experiments.

Multirate Energy-Bounding Algorithm for High-Fidelity Stable Haptic Interaction Control

This brief describes a multirate energy-bounding algorithm that significantly increases the displayable stiffness while guaranteeing the overall haptic interaction stability. Unlike haptic interaction control algorithms that are based on the multirate simulation of virtual environments, the proposed multirate approach separates the low-level control thread from the haptic thread. The haptic thread updates the haptic interaction computation, or the collision detection and response and dynamic or deformation simulation, of a virtual environment at slow rate while the low-level control thread updates the actuator command force determined by the energy-bounding algorithm to guarantee the interaction stability at a high update rate. An analytical derivation study shows that the displayable stiffness of virtual environments can be significantly increased by an order of N, which is the ratio of the fast actuator command signal update to the slow haptic simulation update. Experiments using a commercial haptic device demonstrate that the displayed stiffness significantly increases while guaranteeing stability even when the haptic rendering rate is slow.